1. Field of the Invention
The present invention relates to a profile thermocouple of a transverse-type diffusion furnace used in a diffusion process for semiconductor devices, and more particularly, to a profile thermocouple of a transverse-type diffusion furnace, which is firmly fixed and heat resistant, and which can more stably sense the temperature in the transverse-type diffusion furnace.
2. Background of Related Art
In general, a diffusion furnace is an appliance used in a diffusion process for semiconductor devices, and a thermocouple is employed as a sensor for sensing the temperature in the diffusion furnace.
The thermocouple is made by joining two kinds of metals to each other, e.g., platinum and an alloy of platinum and rhodium, chrome and aluminum, or iron and constantan. In the thermocouple, when there is temperature-difference between the two joined metals, electric current flows therebetween. In this case, the temperature-difference is estimated by measuring the electromotive force generated between the two joined metals.
Usually, the diffusion furnace is classified as a vertical-type or a longitudinal-type diffusion furnace, and a horizontal-type or a transverse-type diffusion furnace. The thermocouple employed in the transverse-type diffusion furnace may be classified as a spike thermocouple or a profile thermocouple. The spike thermocouple is inserted in the diffusion furnace in the transverse direction of the diffusion furnace, so as to sense the temperature of the outer heater. The profile thermocouple is inserted in the diffusion furnace in the longitudinal direction of the diffusion furnace, so as to sense the temperature inside of the inner quartz furnace.
FIG. 1 shows the construction of a conventional profile thermocouple. Referring to FIG. 1, the conventional profile thermocouple includes a plurality of alloy wires 1, a plurality of insulators 2, and a protecting tube or sheath 3 made from quartz. The alloy wires 1, each of which has two different kinds of metals joined to each other, sense the temperature at several portions such as the front, the middle, and the rear portions inside of the transverse-type diffusion furnace. The insulators 2 respectively wrap and insulate each of the alloy wires 1. The protecting tube 3 protects a part of the alloy wires 1 coated with the insulators 2, which protected part is inserted in the diffusion furnace.
Particularly, as shown in FIG. 2, a contact probe 1a protrudes from a distal free end of each alloy wire 1 coated with each insulator 2. The contact probe 1a is thicker than each alloy wire 1.
Referring again to FIG. 1, the conventional profile thermocouple as described above also includes a heat contraction tube 4 fixed to the rear end of the protecting tube 3. The heat contraction tube 4 is made from Teflon. A plurality of extension wires 5 of the alloy wires 1 extend outwardly from the heat contraction tube 4. Each extension wire 5 is connected to a connector 6 which is then connected to a measuring device (not shown).
In the conventional profile thermocouple as described above, the alloy wires 1 wrapped by the insulators 2, the protecting tube 3, and the extension wires 5 are fixed by the heat contraction tube 4, and then the protecting tube 3 is inserted in the diffusion furnace (not shown), so that the temperature in the diffusion furnace may be measured.
However, since the heat contraction tube 4 is located adjacent to the diffusion furnace, the heat contraction tube 4 is apt to be subject to the high temperature heat during the diffusion process. In this case, the heat contraction tube 4 can be burned or melted, causing deformation or damage.
When the heat contraction tube 4 is damaged as described above, the alloy wires 1 may be short-circuited and the temperature in the diffusion furnace can not be precisely measured. Moreover, such a short-circuit may cause the manufacturing system to be disordered or the quality of the manufactured semiconductor devices to be degraded.
Further, since the profile thermocouple is difficult to assemble or disassemble after the alloy wires 1, insulators 2, protecting tube 3, and extension wires 5 are fixed by the heat contraction tube 4, it is difficult to fix and maintain the profile thermocouple. Furthermore, the life of the thermocouple is shortened.